SCIENCE- GOSSIP. 



69 



contains but little 1 Wright red, the results are almost as 

 good as those obtained with the " Absolutus " filter. 

 A very convenient method of using a light filter 

 is to have it mounted in a little brass cap, which 

 will just slip on to the hood of the lens. When 

 mounted in this form it is only a moment's work to 

 put the filter into position, and being outside the 

 camera there is little fear of the filter being left 

 unnoticed when using the ordinary plates. If the 

 ordinary leather cap of the lens is fairly free, the 

 thin brass cap in which the filter is mounted will 

 not interfere with its use in exposure. The working 

 operations of the spectrum plate differ very little 

 from ordinary photography, except that owing to 

 their extreme colour sensitiveness they will not 

 1 >ear exposure to so bright a light in the dark room 

 as the ordinary plate ; but, by taking care to shield 

 the dish during the early part of development, the 

 dark room may still have ample illumination. 



Messrs. Cadett have introduced a safe light for use 

 with their plates, which will enable a much brighter 

 Light to be used than would be safe with the 

 ordinary ruby light, but such a Light, altho 

 very convenient, is not an ;il>vjlute necessity. 



In development it is always advisable to use a 

 developer which will give negatives of a neutral 

 grey colour. Most of the modern developers are 

 suitable, more especially metol and rodinal. 

 Hydrokinone, however, should be avoided, as the 

 image takes some considerable time to appear, 

 and should development be stopped in the earlier 

 stages, there is a liability of the blues being pro- 

 portionally too dense in the negative. With this 

 developer it has been found that the blues of the 

 object appear first, the reds and greens only gaining 

 their proper density after the developer has acted 

 for some considerable time. 



{To be continued.) 



PALAEOLITHIC MAN IN VALLEY OF THE WANDLE. 



By J. P. Johnson. 



rpHE fluviatile and other deposits of the valley 

 -*- of the Wandle were described by Mr. W. 

 Whitaker, B.A., F.E.S., in the "Geology of 

 London," and more recently by Dr. G. J. Hinde 

 in his "Notes on the Gravels of Croydon "('); but 

 no mention is made of the occurrence in them of 

 Palaeolithic implements, and, as far as I am aware, 

 there is only one subsequent record. It is there- 

 fore desirable to draw attention to some further 

 evidence I have obtained of the former presence 

 of Palaeolithic man in this district. In order to 

 illustrate my finds it will be necessary to give a 

 brief account of these deposits, and in so doing to 

 go over some of the ground already dealt with ; 

 but I have much to add that is new. 



The drainage area of the Wandle is bounded on 

 the west by the high ground which divides it from 

 that of the Hog's Mill and Beverley Brooks on 

 the east by the ridge of hills that serjarate it from 

 the valley of the Ravensbourne ; and on the south 

 by a portion of the great chalk plateau known 

 as the North Downs. 



Starting from its source at Croydon, the river 

 first runs westwards, skirting the chalk outcrop, 

 to Carshalton, and then turns abruptly north, con- 

 tinuing along the left margin of the valley, until 

 it enters the Thames at Wandsworth. It there- 

 fore flows entirely through a tract of soft Eocene 

 strata. 



That part of the chalk plateau which constitutes 

 the southern boundary of the above-described 

 district is furrowed by three narrow dry valleys 

 that converge on the river valley at Croydon, and 

 may be considered a southern extension. 



(V) " Trans. Croydon Micro, and Nat. Hist. Club," 1896-7. 



The Palaeolithic drift occurs in two terraces 

 that are separated from one another by a belt of 

 London Clay, except along the course of the Nor- 

 bury Brook, where they are joined together by a 

 thin strip of gravel, which is probably due to 

 subsequent slippage — a process that would be 

 facilitated by the flow of water in that direc- 

 tion. 



The Upper Terrace. — The upper and older 

 terrace, which is wholly on the eastern side of the 

 valley, extends in a straight line from Croydon to 

 Wandsworth Common, where it joins on to the 

 Thames gravels of the same horizon. It is clearly 

 a river-drift, and consists in the main of ochreous 

 subangular flint gravel ; but one meets with flints 

 in every condition of wear, from the well-rolled 

 pebble that has travelled a long distance, to the 

 unworn nodule which has scarcely been detached 

 from the parent rock. They are mixed with a 

 varying proportion of sand and loam, all being the 

 debris resulting from the destruction of the Chalk, 

 the Kentish Tertiaries, the London Clay, and the 

 other strata of the district. There are no stones- 

 that have not been derived from local deposits, 

 though one or two of them are far removed from 

 their original source. The chert, for instance,, 

 which is said to have been detected in this deposit 

 has come by way of the High Level Drifts of the 

 chalk plateau from the outcrop of the Lower 

 Greensand in the Wealden area. No contempo- 

 raneous organic remains have been found in this 

 gravel, for it has been thoroughly decalcified by 

 the action of percolating water. Palaeolithic man 

 has, however, left traces of himself in the shape of 

 " a fine implement nearly eight inches long" found 



